In an Infrastructure as a Service (IaaS) cloud, the capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage selection, deployed applications, and possibly limited control of select networking components (e.g., host firewalls). IaaS clouds primarily offer their users virtual machines (VMs), rather than also software on the VMs (Paas, platform-as-a-service) or even software without access to the VMs (Software-as-a-Service) or business processes (BPaaS).
A Hardware-Infrastructure-as-a-Service (HIaaS) cloud is a sub-division of an IaaS cloud, and provides bare-bones virtual machines as a service. It may also provide an operating system (OS), and even software, but no support is typically provided for the OS or software (e.g., Amazon Elastic Compute Cloud (EC2)). A Managed-Infrastructure-as-a-Service (MIaaS) cloud is a sub-division of an IaaS cloud, and provides full-service virtual machines. The service may, e.g., include OS patching and support for security and compliance of the OS (e.g., IBM SmartCloud Enterprise+ (SCE+) or IBM Cloud Managed Services service available from International Business Machines Corporation, Armonk, N.Y., USA).